Twin Alphas power limit
07-04-2010, 09:37 AM
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Twin Alphas power limit
Hey Guys,
First off, what a great site! We are new to the bigger speed boat world (although ours is small in comparison to what you guys are running) and have been reading through lots of info on the site.
We are a father and son team that picked up a 26' 1986 Wellcraft Nova II recently. The boat is powered with stock twin small blocks and alpha drives with 23P stainless Cleavor props. Our plans are to use it as is for summer, adjusting to the twins (all prior boats were single BB or SB) and addressing some minor cosmetic issues. This winter we are planning to swap out the motors for something a little bit stronger. We are torn between a few repower options, rebuilding the 350s and installing blowers, a pair of 383s, or a pair of 406s. We built the 406s for a customer's boat and he sold the boat before installing. The 383s we would need to build (have good blocks just need the rotating assemblies).
Our concern is that the 406s will send the alphas south quicker than we are ready for it. We have been reading up on the alphas and know their limits (est 350ish). We have also read that in a twin application they work a little less and may survive longer. The 406s are basic performance motors, running around a 9.5:1 compression and put around 350Hp and a little more torque.
Eventually, we will be doing the "right" thing and upgrading to bravos, but for now, we are hoping we can do an engine change this winter and get back out in the spring with some more speed.
Any thoughts or inputs would be greatly appreciated. As for the boat, it has checked out in the survey and everything was good. PO redid stringers and transom and the boat is very solid.
First off, what a great site! We are new to the bigger speed boat world (although ours is small in comparison to what you guys are running) and have been reading through lots of info on the site.
We are a father and son team that picked up a 26' 1986 Wellcraft Nova II recently. The boat is powered with stock twin small blocks and alpha drives with 23P stainless Cleavor props. Our plans are to use it as is for summer, adjusting to the twins (all prior boats were single BB or SB) and addressing some minor cosmetic issues. This winter we are planning to swap out the motors for something a little bit stronger. We are torn between a few repower options, rebuilding the 350s and installing blowers, a pair of 383s, or a pair of 406s. We built the 406s for a customer's boat and he sold the boat before installing. The 383s we would need to build (have good blocks just need the rotating assemblies).
Our concern is that the 406s will send the alphas south quicker than we are ready for it. We have been reading up on the alphas and know their limits (est 350ish). We have also read that in a twin application they work a little less and may survive longer. The 406s are basic performance motors, running around a 9.5:1 compression and put around 350Hp and a little more torque.
Eventually, we will be doing the "right" thing and upgrading to bravos, but for now, we are hoping we can do an engine change this winter and get back out in the spring with some more speed.
Any thoughts or inputs would be greatly appreciated. As for the boat, it has checked out in the survey and everything was good. PO redid stringers and transom and the boat is very solid.
07-05-2010, 08:12 AM
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350hp is pushing the high side for a alpha, if you ease into the throttles and baby them, you may get some time out of them. keep a look out for a set of bravo's though.
07-05-2010, 04:33 PM
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I had a single 406 at least 350hp/400 tq for 10 seasons and the engine gave out before the outdrive. With twins it would be even less stress. You should be fine as long as you don't "floor it" out of the hole everytime. Synthetic drive fluid and drive showers wouldn't hurt either.
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07-08-2010, 11:10 AM
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I had an 87' 26 foot Dana Citation (26' Eliminator V Hull) with a built 454 and Alpha Drive. The boat ran a 22" Bravo 1 prop at 6,200' at a little over 5Krpm at 59mph GPS. Ran it a little over 100 hours no problem but I always took it easy out of the hole.
07-08-2010, 11:19 AM
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Thanks a lot guys for the responses! You have confirmed our thoughts that regular oil changes (with quality oil), drive showers, and taking it easy will help them last until we get the Bravos. Off the top of their heads does anyone know the Bravo Hp/Tq limits?
From what we have read, a Bravo will replace an alpha rather easily and only requires some minor mods to the transom (drilling 2 additional holes if I remember right). I know it isn't a "quick and easy" job, but from what we have read it isn't terribly difficult either.
From what we have read, a Bravo will replace an alpha rather easily and only requires some minor mods to the transom (drilling 2 additional holes if I remember right). I know it isn't a "quick and easy" job, but from what we have read it isn't terribly difficult either.
